USE OF AIR DISPERSION MODELING TO ESTIMATE THE TIME POTENTIALLY AVAILABLE FOR EMERGENCY RESPONSE ACTION NEEDED TO PROTECT PUBLIC SAFETY FROM CHEMICAL RELEASES

by ADKINS, CHRISTOPHER K

Abstract (Summary)

The Release Incorporating Terrain Effects (RITE) Emergency Response Software model was used to determine the amount of time potentially available for emergency response personnel to notify the public and convey instructions on the proper actions that should be taken in the event of a chemical release. The release that was modeled involved chemicals found on occasion in the major rail yard in Cincinnati, Ohio adjacent to Interstate 75. Three chemicals, hydrogen cyanide, chlorine, and ammonia, were used to simulate an accidental release. Meteorological conditions were input to the model to represent a variety of scenarios with each of the three chemicals. The plume travel distance was predicted for each of the chemicals at three concentrations related to occupational exposure, Permissible Exposure Limit (PEL), Threshold Limit Value (TLV), and Immediately Dangerous to Life or Health (IDLH). The distance the plume traveled, used in conjunction with the time frame in which it moved, was used to determine the amount of time available to notify the public. Wind speed did effect the dispersion of the chemicals. Wind speeds below 18 mph, which represents the 95th percentile 24-hour average wind speed, result in the plume covering a greater area, thus exposing larger numbers of people to possibly hazardous conditions. Higher wind speeds, those above 18mph, tend to limit the development and area of the plume at the specified points and result in the plume dissipating at a faster rate. This is due to the increased mixing of the air and the dilution of the chemical at a much higher rate.